Flushed - S9.E11

There are troubles at the Mt Thomas Police Station - the toilet is acting up and the only plumber available is the incompetent Charlie Clarke. But he already has his own set of troubles - his wife is fighting with the new au pair, who it doesn't seem Charlie is paying. But she is clearly not attracted to him so what is her purpose in town? Soon she is linked to a man convicted for fraud who now does sketches, and a murderer on the run and soon lives are at risk. But how can the Heelers prevent anything from happening? It seems that the answers all lie in the station's pipes...